1. Field of the Invention
The present invention relates to exposure devices which are used for manufacturing of semiconductor components and liquid crystal display substrates, for example, by projecting patterns of reticles, to which light sources radiate beams by illuminating area setting means, on photosensitive substrates, and particularly relates to exposure devices, used to perform so-called screen composition in which parts of patterns overlap each other on the photosensitive substrates to form patterns of large areas, as well as devices usable for the exposure devices such as beam shape setting devices, which adjust shapes of beams from illumination sources, and illuminating area setting devices.
2. Background Art
Conventionally, in order to cope with enlargement of the photosensitive substrates which serve as exposed objects, the exposure device of this kind employs a method of screen composition in which an overall exposed area of the photosensitive substrate is divided into multiple unit areas and exposure is repeated in response to each of the unit areas so that desired patterns are formed. In order to perform the screen composition, exposure is performed on exposed areas whose boundaries slightly overlap each other in order to prevent gaps from being formed at boundary positions of the exposed areas due to formation errors of reticles used for pattern projection, aberrations of optical lenses for projection, and errors in positioning of stages used for positioning of the photosensitive substrates.
In general, adjustment of the aforementioned illuminating areas is performed such that reticle blinds are arranged at substantially conjugate positions of the reticles within an optical system of illumination illuminating the reticles. The reticle blind of this kind corresponds to opposed arrangement of units (hereinafter, referred to as blind blades) having two reference sides which are made of metal materials crossing each other, so that openings are set in positions and sizes, that is, illuminating areas are set by moving the blind blades in X-Y directions that cross an optical axis.
However, if such reticle blinds are used and are simply overlapped with the exposed areas, exposure values are doubled with respect to overlapped portions, so some characteristic of photosensitizer may causes variations in line widths of patterns at their joint portions. In addition, when the screen composition is performed, differences in level are caused to occur at the joint portions of the patterns due to positional gaps between the adjoining exposed areas, which may damage characteristics of devices.
In the case where different exposure devices share steps of multilayer composition using patterns of a single layer formed by screen composition with respect to multiple layers respectively, overlapping errors in overlapping the exposed areas of the layers vary discontinuously at joint portions of the patterns due to lens aberrations and positioning accuracy of the exposure devices, wherein particularly in active-matrix liquid crystal display devices, contrasts vary discontinuously at the joint portions of the patterns, so qualities of the devices will be deteriorated.
Therefore, in order to eliminate the aforementioned disadvantages in the screen composition, an exposure device disclosed by Japanese Patent Application, First Publication No. Hei 7-235466 is proposed. In this exposure device, there is arranged a reticle blind 5, which is formed by overlapping two sheets of blinds 5A, 5B as shown in FIG. 10A at optically conjugate positions with respect to the reticle, wherein it is possible to obtain a pattern of a necessary extinction area by matching openings 23, 25 of the blinds 5A, 5B together, further, it is possible to match an irradiation range of illumination light with a size of the reticle by changing sizes of the openings, which is actualized by changing relative positions of the blinds 5A, 5B.
The reticle blind 5 is formed by arranging the blinds 5A, 5B, each of which has two openings and whose chrome surfaces face with each other, in proximity to each other in an order of 100 xcexcm. In addition, each of the blinds 5A, 5B is formed by vapor deposition in which chrome is deposited on a transparent glass substrate and is equipped with a shade portion 21 for shade of illumination light, extinction portions 22, 24 for attenuation of transmission factors of illumination light and openings 23, 25 on which chrome is not deposited.
In the extinction portions 22, 24, a chrome film corresponds to dots, each of which is smaller than a resolution limit of the exposure device, and are deposited on the glass substrate, wherein a density of the dots of the chrome film is increased in a direction from the opening 23 to the shade portion 21 (or from the opening 25 to the shade portion 21) so that an extinction factor is changed with respect to the extinction portion 22 or 24. FIG. 10B and FIG. 10C show extinction characteristics with respect to one blind 5A or 5B of the reticle blind 5. By overlapping adjoining exposed areas in the extinction portions 22, 24, the joint portions of the patterns change smoothly.
However, the aforementioned reticle blind 5 requires the transparent substrate like the glass as the base for formation of the extinction portions 22, 24, so if particles whose diameters are greater than a certain diameter are adhered to the glass substrate of the reticle blind 5 at its openings 23, 25 or extinction portions 22, 24, there is a problem that the particles originally adhered on the glass substrate of the reticle blind 5 are transferred to the photosensitive substrate because the reticle blind 5, reticle and photosensitive substrate are arranged at optically conjugate positions.
For this reason, the conventional device is equipped with a particle detector which detects adhesion of the particles by projecting detection light such as mercury light on Cr-deposited surfaces and measuring amounts of scattering light which occurs, so the construction of the device must be complicated.
In addition, the aforementioned particle detector is capable of performing detection on a front surface of a glass plate but is hard to project the detection light on a back of the glass plate due to construction thereof, so it is actually incapable of detecting existence of foreign matters to be existed on the back of the glass plate.
The present invention is made in consideration of the aforementioned problems, and it is an object of the invention to provide an exposure device, which is capable of preventing particles from being transferred to a photosensitive substrate and which does not require a particle detector, as well as a beam shape setting device used for the exposure device.
In order to achieve the aforementioned object, an exposure device of the present invention, which has an illumination optical system for illuminating a reticle having a pattern with a beam from an illumination source so that the pattern is formed on a substrate on exposure to light, is equipped with illuminating area setting means, which are arranged at two locations in the illumination optical system so as to set an illuminating area of the beam illuminating the reticle, and an optical system which places the illuminating area setting means being conjugate to the reticle.
In addition, a beam shape setting device of the present invention, which has a transmission portion for transmitting a beam therethrough and a shade portion for shade of the beam so as to set a shape of the beam, is equipped with a protection member which covers the transmission portion with a material that transmits the beam.
The beam shape setting device of the present invention can be equipped with an extinction portion, which is arranged in at least a part of an area between the transmission portion and the shade portion and which reduces a transmission factor of the beam to be smaller in a direction from the transmission portion to the shade portion. In this case, it is possible to smoothly connect joints of patterns of screen composition.
In this case, it is possible to provide a transparent base material, so the shade portion is formed by a shade member mounted on the transparent base material, the transmission portion is formed by an opening formed on the transparent base material, and the extinction portion is formed such that a density of the shade member on the transparent base material is increased to be larger in a direction from the transmission portion to the shade portion. In this case, it is possible to form the transmission portion and extinction portion with simple constructions.
In addition, the exposure device of the present invention can use the beam shape setting device as the illuminating area setting means.
In addition, the illuminating area setting device of the present invention is the illuminating area setting device which sets an illuminating area of the beam by using a shade portion for shade of at least a part of the beam in a side of a front surface of the transmitting portion for transmitting the beam therethrough and which is equipped with a cover plate which transmits the beam and which forms a closed space corresponding to a predetermined space in a side of a back surface of the transmission portion.
Therefore, the illuminating area setting device of the present invention is capable of setting an illuminating area of the beam by using the shade portion with respect to the beam which transmits through the transmission portion and cover plate. The cover plate forms the closed space in the side of the back surface of the transmission portion, so it is possible to prevent foreign matters from being attached to the transmission portion.
Thus, the illuminating area setting device is capable of preventing the foreign matters from being attached to the back surface of the transmission portion, while the cleaning operation is required with respect to only the front surface to which the foreign matters are being attached, so it is possible to obtain an effect in reduction of the maintenance time.
The illuminating area setting device can be constructed such that the closed space is formed by a holding member for holding the back surface of the transmission portion and the cover plate. In this case, it is possible to form the closed space in the side of the back surface of the transmission portion with ease by merely providing the cover plate, which offers effects in preventing the foreign matters from being attached to the back surface of the transmission portion and in reduction of the maintenance time.
The illuminating area setting device can be constructed such that cover plates are arranged with respect to multiple transmission portions respectively. In this case, even if there are arranged multiple transmission portions, it is possible to obtain a superior effect in preventing the foreign matters from being attached to the back surfaces of the transmission portions respectively.
An exposure device of another embodiment of the present invention is the exposure device in which a light source radiates a beam on a reticle by an illuminating area setting device so that a pattern of the reticle being illuminated is transferred to a photosensitive substrate, wherein it is characterized by that as the illuminating area setting device, the aforementioned illuminating area setting is used such that the front surface of the transmission portion is located in proximity to a conjugate plane of the reticle, so that an illuminating area of the beam being radiated to the reticle is set by the illuminating area setting device.
In this exposure device, a closed space is formed in a side of a back surface of the transmission portion, so that it is possible to prevent foreign matters from being attached to the back surface of the transmission portion, and it is possible to prevent images of the foreign matters from being transferred onto the photosensitive substrate. In the case where the foreign matters are attached to the back surface of the transmission portion, they are attached to the cover plate as well, however, the cover plate is arranged being apart from the conjugate plane of the reticle by a distance corresponding to the closed space, so it is possible to prevent images of the foreign matters from being formed on the photosensitive substrate.
Therefore, the foreign matters are not attached to both of the surfaces of the transmission portion, so it is possible to obtain an effect that a pattern of the reticle can be certainly transformed onto the photosensitive substrate in accordance with prescribed procedures. Even if the foreign matters are attached to the cover plate, it is possible to avoid nonuniformity of illuminance, which causes a problem with respect to the photosensitive substrate, and it is possible to prevent images of the foreign matters from being transferred onto the photosensitive substrate, wherein even if parameters constructing the optical characteristics are changed, it is possible to obtain an effect in adequately setting a separation distance between the conjugate plane of the reticle and the cover plate on the basis of expected sizes of the foreign matters.
The exposure device of the present invention can be equipped with a foreign matter inspection device for performing detection as to whether foreign matters are attached to the surface of the transmission portion or not. Thus, the exposure device is capable of performing detection on the front surface of the transmission portion in which the foreign matters are not attached to the back surface, so during an exposure mode, it is possible to perform the setting of the illuminating area under conditions where no foreign matters are attached to both of the front and back surfaces of the transmission portion, so it is possible to obtain a superior effect in accuracy of transferring the predetermined pattern formed on the reticle to the photosensitive substrate.